PURPOSE: To simplify design changing operation.

CONSTITUTION: By forming the cam contact part 40 of a slider 28 s< that it may be protruded in the direction where the start of closing a cassette front door 44 is delayed, the cam contact part 40 is abutted on a cam surface 90a for opening a door at a holder moving position where cassettes L, M and S in a cassette holder 56 are partially faced to the anti-cassette insertion side of a door opening/closing locus just before closing the front door 44 is started. Therefore, at the time of ejecting the cassette. the closing action of the front door 44 is started after the cassettes L, M and S are partially faced to the anti-cassette insertion side of the door opening/closing locus, so that the closing start timing of the front door 44 is corrected by changing the shape of the slider 28.